Hi Richard, I added both the v2 (slightly enhanced v1) and v3 (which uses the enum). I have to say that I prefer v2 a lot more than v3 - the enum just makes it worse in my opinion (maybe I just "implemented it wrong") - tell me what you think. Thanks! On Tue, Mar 16, 2021 at 12:36 PM Sam Eiderman <sameid@google.com> wrote:

By using:

export LIBGUESTFS_BACKEND_SETTINGS=force_kvm

you can force the backend to use KVM and never fall back to TCG (software emulation). --- lib/guestfs-internal.h | 3 +++ lib/guestfs.pod | 9 +++++++++ lib/launch-direct.c | 42 ++++++++++++++++++++++++++++++++++++------ lib/launch-libvirt.c | 29 ++++++++++++++++++++++++----- 4 files changed, 72 insertions(+), 11 deletions(-)

diff --git a/lib/guestfs-internal.h b/lib/guestfs-internal.h index 43509c6db..97dacc2b8 100644 --- a/lib/guestfs-internal.h +++ b/lib/guestfs-internal.h @@ -157,6 +157,9 @@ guestfs_int_cleanup_gl_recursive_lock_unlock (void *ptr) #define VIRTIO_DEVICE_NAME(type) type "-pci" #endif

+/* Guestfs accel options. */ +enum accel { BEST_ACCEL, FORCE_TCG, FORCE_KVM }; + /* Guestfs handle and associated structures. */

/* State. */ diff --git a/lib/guestfs.pod b/lib/guestfs.pod index bce9eb79f..ff58aa0bb 100644 --- a/lib/guestfs.pod +++ b/lib/guestfs.pod @@ -1530,6 +1530,15 @@ Using: will force the direct and libvirt backends to use TCG (software emulation) instead of KVM (hardware accelerated virtualization).

+=head3 force_kvm + +Using: + + export LIBGUESTFS_BACKEND_SETTINGS=force_kvm + +will force the direct and libvirt backends to use KVM (hardware +accelerated virtualization) instead of TCG (software emulation). + =head3 gdb

The direct backend supports: diff --git a/lib/launch-direct.c b/lib/launch-direct.c index b6ed9766f..416a87fa0 100644 --- a/lib/launch-direct.c +++ b/lib/launch-direct.c @@ -385,6 +385,9 @@ launch_direct (guestfs_h *g, void *datav, const char *arg) struct hv_param *hp; bool has_kvm; int force_tcg; + int force_kvm; + enum accel accel; + const char *accel_val; const char *cpu_model; CLEANUP_FREE char *append = NULL; CLEANUP_FREE_STRING_LIST char **argv = NULL; @@ -434,8 +437,35 @@ launch_direct (guestfs_h *g, void *datav, const char *arg) if (force_tcg == -1) return -1;

- if (!has_kvm && !force_tcg) - debian_kvm_warning (g); + force_kvm = guestfs_int_get_backend_setting_bool (g, "force_kvm"); + if (force_kvm == -1) + return -1; + + if (force_kvm && force_tcg) { + error (g, "Both force_kvm and force_tcg backend settings supplied."); + return -1; + } + else if (force_tcg) { + accel = FORCE_TCG; + accel_val = "tcg"; + } + else if (force_kvm) { + accel = FORCE_KVM; + accel_val = "kvm" + } + else { + accel = BEST_ACCEL; + accel_val = "kvm:tcg"; + } + + if (!has_kvm) { + if (accel != FORCE_TCG) + debian_kvm_warning (g); + if (accel == FORCE_KVM) { + error (g, "force_kvm supplied but kvm not available."); + return -1; + } + }

/* Using virtio-serial, we need to create a local Unix domain socket * for qemu to connect to. @@ -527,13 +557,13 @@ launch_direct (guestfs_h *g, void *datav, const char *arg) append_list (MACHINE_TYPE); #endif #ifdef __aarch64__ - if (has_kvm && !force_tcg) + if (has_kvm && accel != FORCE_TCG) append_list ("gic-version=host"); #endif - append_list_format ("accel=%s", !force_tcg ? "kvm:tcg" : "tcg"); + append_list_format ("accel=%s", accel_val); } end_list ();

- cpu_model = guestfs_int_get_cpu_model (has_kvm && !force_tcg); + cpu_model = guestfs_int_get_cpu_model (has_kvm && accel != FORCE_TCG); if (cpu_model) arg ("-cpu", cpu_model);

@@ -690,7 +720,7 @@ launch_direct (guestfs_h *g, void *datav, const char *arg) }

flags = 0; - if (!has_kvm || force_tcg) + if (!has_kvm || accel == FORCE_TCG) flags |= APPLIANCE_COMMAND_LINE_IS_TCG; append = guestfs_int_appliance_command_line (g, appliance, flags); arg ("-append", append); diff --git a/lib/launch-libvirt.c b/lib/launch-libvirt.c index eff1c8f7e..b8ad8d265 100644 --- a/lib/launch-libvirt.c +++ b/lib/launch-libvirt.c @@ -772,6 +772,8 @@ parse_capabilities (guestfs_h *g, const char *capabilities_xml, xmlAttrPtr attr; size_t seen_qemu, seen_kvm; int force_tcg; + int force_kvm; + enum accel accel;

doc = xmlReadMemory (capabilities_xml, strlen (capabilities_xml), NULL, NULL, XML_PARSE_NONET); @@ -819,11 +821,30 @@ parse_capabilities (guestfs_h *g, const char *capabilities_xml, } }

+ force_tcg = guestfs_int_get_backend_setting_bool (g, "force_tcg"); + if (force_tcg == -1) + return -1; + + force_kvm = guestfs_int_get_backend_setting_bool (g, "force_kvm"); + if (force_kvm == -1) + return -1; + + if (force_kvm && force_tcg) { + error (g, "Both force_kvm and force_tcg backend settings supplied."); + return -1; + } + else if (force_tcg) + accel = FORCE_TCG; + else if (force_kvm) + accel = FORCE_KVM; + else + accel = BEST_ACCEL; + /* This was RHBZ#886915: in that case the default libvirt URI * pointed to a Xen hypervisor, and so could not create the * appliance VM. */ - if (!seen_qemu && !seen_kvm) { + if ((!seen_qemu || accel == FORCE_KVM) && !seen_kvm) { CLEANUP_FREE char *backend = guestfs_get_backend (g);

error (g, @@ -841,11 +862,9 @@ parse_capabilities (guestfs_h *g, const char *capabilities_xml, return -1; }

- force_tcg = guestfs_int_get_backend_setting_bool (g, "force_tcg"); - if (force_tcg == -1) - return -1; + assert((accel != FORCE_KVM) || seen_kvm);

- if (!force_tcg) + if (accel != FORCE_TCG) data->is_kvm = seen_kvm; else data->is_kvm = 0; -- 2.31.0.rc2.261.g7f71774620-goog